Two key messages have emerged from long-term windrow burning trials in Western Australia’s northern wheatbelt – focus on trash from non-cereal crops and burn in the daytime where possible.
Rod Messina, whose family farming business “Spring Park Farms” has hosted windrow trials for more than a decade, says the practice has underpinned their property expansion.
“We find that when we buy a new property it always has a lot of weeds but after two or three years of integrated weed management (IWM) practices including burning windrows, it’s amazing how quickly weed numbers come down,” Rod said.
“Weeds dictate what we do here, they’re our number one issue. So if a paddock’s dirty, rotation becomes vital and ultimately allows us to continuously crop.
“It is quite expensive to leave paddocks out of production so with the rotation and windrow burning it allows our operation to be more profitable in the long run.”
Rod farms 12,500 hectares with his father Charlie and brother Andrew on the Eradu sandplain east of Geraldton.
They employ a wheat/lupin/wheat/canola rotation and strategically use herbicides to control radish in the cereal phase while windrowing canola and lupin crops to collect and destroy hard-to-kill wild radish seed.
“Wild radish is one our most problematic weeds. We do have ryegrass but radish is our biggest concern because the seed is viable for so long,” Rod said.
“In our lupin and canola phases we try to make sure we control all the seed set either through windrow burning or crop-topping.
“We try to get a germination of wild radish before we sow but in this environment that is not always possible.
“There is no doubt through our long-term IWM strategy, including windrow burning, autumn tickles, crop-topping, a double knock and now the mouldboard plough, that our weed numbers are decreasing.”
The Messinas aim to stop seed set at every stage of the crop production and weed life cycle.
“We deep rip to stimulate a germination of weeds that we can treat with a knockdown herbicide or double knock, then we’ll use one, maybe two post-emergent sprays followed by crop-topping lupins and windrow burning.”
The Messinas have trialled a mouldboard plough and spading but chose to go with the mouldboard plough for its weed and non-wetting soil management benefits.
Rod says the practice of windrowing as demonstrated by the GRDC-supported work by Department of Agriculture and Food WA (DAFWA) weed researcher Peter Newman has been proven over more than a decade.
“The numbers are declining quite rapidly and one of the greatest benefits of windrowing is that it doesn’t slow harvest at all,” he said.
“The hotter the fire the better it is and through the GRDC focus paddocks we’ve learnt that you do need a much hotter fire to control wild radish than for ryegrass.
“We have to try and get the fire as hot as possible. It’s easy in lupins and canola because there is less chance of the fire spreading than in wheat so you can light the windrows up during the day and make sure you get a really hot burn.
GRDC/DAFWA plots across the district are achieving 99% control of weeds using windrow burning.
“In an ideal world you wouldn’t windrow your wheat because there is a chance you’ll lose the paddock but in a lighter year like this year we’ve windrowed all the paddocks in order to use that tool.”
Rod says a cereal crop of more than two and a half tonne per hectare is too dense for windrowing due to the risk of burning the whole paddock and losing valuable soil cover.
“If you’ve got a really dense windrow the fire will run across the top and won’t penetrate the windrow and research shows some of the seed falls to the bottom within about 24 hours.”
He advocates burning late in the day rather than at night as the intensity of the fire drops as the temperature falls.
“Five to seven years ago we windrowed every acre but now that we’ve got our numbers down we can just do the lupins and canola phases,” he said.
“There is more opportunity to control wild radish during the wheat phase using herbicides and other tools and can manage the ryegrass during the non-cereal phases.”